A device known in the related art, which adjusts the charge levels of a plurality of battery cells constituting an assembled battery in order to reduce variance among residual charge levels (cell balancing) and executes charge level adjustment when the assembled battery has not been used over a predetermined length of time (PTL 1).
The battery control system disclosed in PTL 1 comprises a battery control unit that is connected to the assembled battery and includes a CMOS timer IC and a system control unit that includes a microcomputer that receives power provided from a battery other than the assembled battery. The microcomputer calculates the length of time over which the charge level adjustment is to be executed, the length of time thus calculated is transferred to the CMOS timer IC and the charge level adjustment operation starts. Since the battery control unit, to which power is provided from the battery cells constituting the assembled battery, receives the length of time over which the charge level adjustment is to be executed transmitted thereto before the charge level adjustment operation starts, the charge level adjustment operation can be continuously executed even after the power supply to the microcomputer side stops.